This invention relates generally to electrostatographic reproduction machines, and more particularly to an adaptive roll for reliably feeding sheets of various sheet weights generating various different tangential resistance forces to feeding.
Traditionally, sheet feeding rolls are employed in friction retard type sheet feeding and supply apparatus to move the top sheet from a stack of such sheets to a retard mechanism as a result of a net frictional force. The retard mechanism then allows a single substrate or sheet at a time to pass through the retard mechanism. Some such sheet feeding rolls are constructed from an elastomeric material. These rolls have a relatively high failure mode from loss of a suitable friction coefficient due to contamination, dirt build-up as well as from wear and tear.
Other such sheet feeding rolls are in the form of a series of studded metal pin wheels which act to grab or stick the top sheet in the stack and move it into the friction retard mechanism. A studded roll of this type works well for most substrate or sheet types, and has a long roll life, however, the studded roll does not handle high density substrates or sheets very well due to an ability to penetrate the surface of such substrates or sheets. Also, the studded roll does not handle transparencies satisfactorily. Further, the studded roll may leave scratch marks on the surface of substrates or sheets fed at high feed rates.
When a rotating roll is used to feed the sheet or paper by a frictional force between the sheet and roll, the maximum available feed force is determined by the product of the normal force and the coefficient of friction between the roll and the sheet which could be paper, transparencies, etc. Because the coefficient of friction is uncertain in nature, the maximum available feed force is mainly controlled by the normal force. That is, as the required feed force increases due, for example, to increases in sheet weight and stiffness, the normal force should also increase adaptively or be increased responsively in order to maintain reliable feeding.
Unfortunately, in most machines that use sheet feeding apparatus including sheet feeding rolls, the normal force is typically set to a fixed optimum value to meet the particular design requirements, additional expensive compensating components have to be included with the sheet feeding rolls for attempting to vary the normal force. Sheet feeding deficiencies such as sheet misfeeds and multi-feeds are still common.
Accordingly, in an aspect of the present invention, there is provided a self-adaptive sheet feeding roll for reliably feeding, within a sheet feeding apparatus, sheets of various and different sheet weights along a sheet path. The self-adaptive sheet feeding roll includes (a) a cylindrical core having a longitudinal axis and an outer surface; (b) a compliant surface layer formed over the outer surface of the cylindrical core and having an external surface and a given layer thickness; and (c) a series of spaced apart, nonradial slots formed from the external surface into the compliant surface layer and defining a series of spaced apart blade portions within the compliant surface layer for adaptively compressing and deforming against, and responsively to, sheets of various and different sheet weights, thereby self-adjusting a normal force Fn as well as a sheet driving force Fd thereof and enabling reliable feeding, within a sheet feeding apparatus, of such sheets of various and different sheet weights.